On Fri, 29 Oct 2004 02:39:55 -0400, Wayne.B
wrote:

On Thu, 28 Oct 2004 22:00:46 -0400, "Glenn Ashmore"
wrote:

There is a tow behind RO watermaker called the Waterlog that uses
a small mechanical pump powered by a propellor. Though JAX claims them to
be mythical I met two cruisers in the BVI who used them all the way from
Gibralter and were very happy with their performance.

============================

72 gpd:

http://www.watermakers.ws/

50 gpd = $2 grand....

Brian W

"Glenn Ashmore" wrote in message
news:7vhgd.80763$hj.25297@fed1read07...
Actually you only need 800 PSI

You can certainly do it with far less than that. A home RO unit runs off the
water line pressure, which is usually less then 75 PSI.

which is still way past what a ram pump can produce.

There are always ways to convert a flow of water and one pressure to a
lesser flow at higher pressure. You might have better output running a
solar still, however.

There is a tow behind RO watermaker called the Waterlog that uses
a small mechanical pump powered by a propellor.

There are a lot of instances of a towed electrical generator. It certainly
would not be conceptionally difficult to convert it into a water pump. I
can picture a small prop on a steel cable that runs up to a gear box on the
transom rail. Enough gear ratio can turn the spinning cable into sufficient
torque to generate just about any PSI you wanted.

I would think that you would be better off to just generate electricity and
then run the standard electric pump. Perhaps not as efficient, but much more
versatile.

Rod

"rmcinnis" wrote in message
...

Actually you only need 800 PSI

You can certainly do it with far less than that. A home RO unit runs off
the
water line pressure, which is usually less then 75 PSI.


Osmotic pressure is directly related to the concentration of salts in the
water. Tap water has a maximum concentration of 200 PPM salt so that the
pressure is about 10 PSI. Seawater OTOH at 36,000PPM salt and 68F has an
osmotic pressure of about 376 PSI. That is just enough pressure to STOP the
osmosis of salt into the low concentrate side. To REVERSE the osmosis
requires more pressure. Generally double or about 750 to 800 PSI.

(When you build your own watermaker you learn a lot of normally useless
stuff. :-) )

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
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